These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Home Improvement
Acceptable Targets: The overweight; however, Tim's restriction of his fat jokes to Al, Al's mother, and Jill's mom (before she lost weight) may have been meant to imply it's only all right if it's a friend and they know you're joking (though judging by Al's reaction, they don't have to think it's funny).
It should be noted that at Al's mother's funeral, it was revealed that she thought Tim's fat jokes were Actually Pretty Funny.
Crosses the Line Twice: When Tim asked an exterminator who used nerve gas what's shaking, Wilson answers his entire body.
Al is this in universe as well with Tool Time: Most fans of the show that meet Tim usually tell him how much they love or idolize Al, or they will confuse Al for being the star of the show. This always annoys Tim.
Wilson, too. Originally, the character had limited screentime that was simply to have Tim seek advice on his current problem. However, producers liked both actor and character, so they gave him increasingly more to do over the run of the show. (Episodes centered around him, regular interactions with the other characters, a love interest, etc.)
Tool Time itself was this. A number of fans actually enjoyed the home-project-slapstick more than the actual sitcom.
Pat: Home Improvement shouldn't've been the show. Tool Time should've been the fucking show.
Fridge Horror: When Randy goes upstaris to study with his girlfriend, Tim and Jill reminisce about how their own study sessions used to lead to sex...and a split second later they go check on Randy and the girl over the end credits.
Hilarious in Hindsight: In the series finale Tim introduced Al as "Al-be-doing-infomercials-for-a-living Borland!" Richard Karn is indeed doing infomercials now, in costume as Al.
A 1993 episode (more accurately, the episode where Randy breaks his wrist sliding down Dead Man's Curve) features an easy-to-miss line where a character named Buzz brings Tim his coffee, "just how he likes it, cream and five sugars" Buzz then says "Two more sugars, they'll be calling you Buzz!" Then consider what Tim did two years later...
When Al lets the fame over being named one of Detroit's sexiest bachelors get to his head, Tim is in disbelief over Al's audacity to splurge on a luxury: a cell phone.
When Mark goes trick or treating as Tim during season 2's Halloween episode, Randy tells him he would get more candy if he dresses up as Al. Two years later, he does just that and wins a sack of candy at a costume contest where Al's mom was the judge.
Seanbaby: This is a screenshot of a man with a grappling hook fighting a dinosaur. I swear to God this is based on the family show with the same name.
Even more infamous is the fact that the manual is just a folded sheet of paper with "REAL MEN DON'T NEED INSTRUCTIONS" plastered over fake manual text, which might be mildly amusing if the game weren't so confusing and in desperate need of an actual manual.
Recycled Script: "Bewitched" the final Halloween Episode of the show, feels very similar to season 3's "Crazy Over You." Both episodes involved nearly the entire cast secretly joining forces to play an elaborate Halloween prank on Tim in retaliation for his crazy amounts of pranks, and both episodes even conclude with similar stingers of Tim getting some minor revenge by playing one last prank on the respective masterminds.
Seinfeld Is Unfunny / So Okay, It's Average: The show itself was popular for its time, but in hindsight even members of the cast have admited that the formula of the show was very generic, and that it really did nothing to try to push any boundaries or introduce anything that had not been seen in any of the other many sitcoms popular at the time.
Tropes Are Not Bad: As evidenced by the show's huge success during its initial run and continued syndication.
Tear Jerker: The episode when Jill's dad died. Another example is John Binford's death. Even moreso when Wilson gives Tim a small speech about grieving, to which he ends by saying, "It lets you accept that the person is really... truly... gone." Tim looks over the fence, and finds Wilson has left Tim by himself. After Earl Hindman, Wilson's actor, died in 2003, this scene was just so much worse.
"The Longest Day" where they think Randy might have cancer. When Randy breaks down while talking to Tim at the arcade and then jumps into Tim's arms.
"Why does this bad stuff always have to happen to me?...I don't wanna die, Dad."
The episode where Al's mother dies. Doubles as bittersweet heartwarming during Tim and Al's speeches at her funeral: Despite all Tim's fat jokes and Al's griping about how she smothered him, Al really loved his mother and Tim was aware of all her great qualities.
Well-Intentioned Extremist: Probably one of the most benign examples ever, but Tim would always be obsessed with making simple or menial things hyper-masculine, or as he puts, giving it "more power" in order to improve it. As a Running Gag in the series, this almost always led to whatever project he's making more manly to blow up in his face (literally) but he still continues his obsession throughout the series.
The Woobie: Mark, in early seasons. God, his big brothers were such pricks.
It never seemed to bother him all that much though, and Brad and Randy usually suffered for the teasing.
Mark kind of remained The Woobie even into his teen years. Because of his oddball habits and interests (and briefly becoming a goth), he often had difficulty keeping a girfriend.
Jerkass Woobie: Randy was an insufferable smartass, but several episodes showcased his hidden insecurities (his small size, worrying about how "cool" he was to girls, thinking Brad was their father's favorite) or gave him serious issues to cope with ("The Longest Day" in which he thought he might have cancer and "Losing My Religion" in which an old woman he bonded with suddenly became ill).
Brad (and by extension his actor, Zachary Ty Bryan) actually could be The Woobie on a meta level during the last half of Season 5 through the end of Season 7. In Season 5, Brad had some Character Development to start becoming a good student at the same time, Johnathan Taylor Thomas's character, Randy skipped two grades to join Brad in High School as to enable the two of them to have High School plotlines together. Unfortunately, JTT's career really took off at that time and combined with his more intellectual character and strong episodes like The Longest Day or the one where he wrote a big paper article slamming Tim's employer Binford, he started to overshadow Brad, who mainly got stuck with romantic or sports storylines. Taylor's departure for Season 8 ultimately allowed Brad and Zachary Bryan to get a season in the limelight dealing with him prepping for college.